In a known vibration exciter with two unbalanced weights, a pin is used for the purpose of the adjustment of the phase position of the unbalanced weights, which pin engages in a groove of a hub extending in a screw-like manner. A translational movement of the pin causes a rotary movement of the hub, so that mutual twisting of the unbalanced weights is enabled. It is disadvantageous that high adjusting forces need to be applied in this case. It is a further disadvantage that a complex coupling needs to be provided between the unbalanced weights. This not only leads to higher costs, but also to a need for a more space.
A counter-rotating vibrator is also known, in which the exciter power can be set continuously during operation. For this purpose, a planar coupling gear is used as a planar oscillating slider. A displacement of the slide rod leads to an oscillating movement of the coupler and the crank, so that the distance of the centers of gravity of the unbalanced weights can be varied in relation to the rotational axis of the unbalanced shaft. In this case too there is a disadvantage that the vibration exciter requires a relatively large installation space both in the axial and the radial direction of the unbalanced shaft on the basis of its principle because the outward vibration of the unbalanced weights in the radial direction is required for increasing the exciter power.